Learn Spanish (Latin America): Cambiar la bobina con cuidado.

In Spanish, the infinitive is often used for impersonal commands, written instructions, or signs where the writer isn't addressing a specific person. You will frequently see this in manuals, recipes, or on packaging.

Could this sentence be made negative simply by adding no?

Yes! For impersonal instructions using the infinitive, you just put no right in front of the verb. If the manual wanted to warn you against doing this, it would say No cambiar la bobina.

Is bobina a sewing term or a mechanical term here?

It can be both! A bobina refers to a spool, reel, or coil. This instruction could easily belong to a sewing machine manual (changing the thread bobbin) or a car maintenance guide (changing the ignition coil).

Could I use the adverb cuidadosamente instead of the phrase con cuidado?

You could, and it would be grammatically correct. However, Spanish speakers generally prefer using con plus a noun (like con cuidado or con paciencia) over adverbs ending in -mente, because it often sounds more natural and flows better.